1. Technical Field
The disclosure relates to a magnetic memory technology. More particularly, the disclosure relates to a magnetic shift register memory which conducts a domain wall motion technique.
2. Background
Research and development on conventional magnetic memories have been conducted for years. Moreover, theories and experiments regarding current-driven domain wall motion have proceeded maturely in recent years. In U.S. Pat. No. 6,834,005, a device structure referred to as a magnetic shift register capable of significantly increasing data storage capacity of chips or hard drives was disclosed. The magnetic shift register possibly replaces the existing dynamic random access memory (DRAM), the existing static random access memory (SRAM), and the existing flash chip. Moreover, the magnetic shift register realizes the concept of a “disk drive on a chip”. In the magnetic shift register, a magnetic recording hard disk drive similar to the common hard drive is employed to record data one by one through current-driven domain wall motion. Since the magnetic shift register uses the stack structure to store data in a vertical memory track which occupies little space on the substrate, the magnetic shift register can be built with reducing for the equivalent bit size, and access speed of the magnetic shift register exceeds that of the conventional flash memory chip and hard drive.
FIG. 1 is a schematic view illustrating a conventional magnetic shift register designed by implementing a current-driven domain wall motion mechanism. As shown in FIG. 1, there is a plurality of magnetic domains 102 on a memory track 100. Each of the magnetic domains 102 has a magnetization direction to correspondingly store one bit of data, such as “0” or “1”. a magnetization direction of. When binary data stored in adjacent two of the magnetic domains 102 are different, the two magnetic domains 102 then have opposite directions of magnetic moment, and a domain wall 104 is formed. By applying an electronic current flow I, the domain wall 104 moves in the direction of the current flow I, and thereby also moves the magnetic domains 102 in the memory track 100. When the magnetic domains 102 pass across a reading device 106 or a writing device 108, the data on the magnetic domains 102 can be read by the reading device 106 or written by the writing device 108 at the magnetic domains 102.
Nevertheless, further research and development are directed to improvement of memory device performance in order to effectively and accurately write data in the magnetic domains and simultaneously stabilize the device.